Sanitary Sewer Trunk System

Challenge

This rapidly growing community located in the heart of the Des Moines metro area needed to plan for future development while remaining vigilant about the existing needs of their infrastructure.

Smart development was of paramount importance to the city of Ankeny. Anticipated areas of development encompassed approximately 18 square miles north of the corporate limits. How to best serve the sanitary sewer needs of this area was a tough question for the city.

Solution

FOX was selected as the engineering consultant for planning, design, and construction administration of Ankeny’s sanitary sewer trunk mains to serve anticipated development areas and reliably move waste for an area approximately 18 square miles in size. FOX worked with the city to define watershed areas and wastewater loadings, and evaluated the existing downstream sewer to determine available capacity. This data was used to complete preliminary design of the sanitary sewer trunk system which included preferred routing and anticipated pipe sizes and slopes.

Outcome

The study has allowed Ankeny to approve sewer extension requests from developers and to design portions of the trunk system as needed without further evaluations. In addition, FOX designed and provided construction services for three portions of the trunk sewer system. The Four Mile Creek Trunk Sewer had a construction cost of $940,000 and consisted of 2,700 feet of 30-inch sanitary sewer and 7,915 feet of 15-inch and 12-inch sanitary sewer. The project included a 285-foot 30-inch bore of gravity sewer under US HWY 69 and several Four Mile Creek crossings. The Otter Creek Trunk Sewer construction cost was $400,000 and consisted of 4,600 feet of 24-inch sanitary sewer with several Otter Creek crossings. FOX completed the third phase of the trunk sewer extension in 2011. The second Four Mile Creek sewer designed by FOX had a construction cost of $184,000 and consisted of 470 feet of 30” sanitary sewer including a crossing of Four Mile Creek.